Molecular aspects of the interaction of spermidine and α-chymotrypsin

Polyamines such as spermidine are essential for survival. The purpose of the present study was to investigate how spermidine could influence the conformation, thermal stability and the activity of α-chymotrypsin. The influence of spermidine on the structure and stability of α-Chymotrypsin (α-Chy) explored using different spectroscopy method and molecular docking simulations. The stability and activity of α-Chy were increased in the presence of spermidine. Increasing of the α-Chy absorption in the presence of spermidine was as a result of the formation of a spermidine - α-Chy complex. The results of fluorescence spectroscopic measurements suggested that spermidine has a vigorous ability to quench the intrinsic fluorescence of α-Chy through the dynamic quenching procedure. Near and Far-UV CD studies also confirmed the transfer of aromatic residues to a more flexible environment. The absorption increasing of α-Chy in the presence of spermidine was as a result of the formation of spermidine - α-Chy complex. Molecular docking results also revealed the presence of one binding site with a negative value for the Gibbs free energy of the binding of spermidine to α-Chy. Further, the docking study revealed that van der Waals interactions and hydrogen bonds play a main role in stabilizing the complex.